1. Field of the Invention
This invention is in the field of expandable chucks for supporting a roll of web material such as paper for winding or unwinding. The chuck of the present invention uses a one-piece expanding member which provides its own retaining action and has a plurality of expanding elements which engage the inner diameter of the roll core. The expanding elements are actuated by hydraulic pressure operating through a spindle and against a piston to provide tight engagement between the expanding elements and the inner diameter of the roll core.
2. Description of the Prior Art
When paper is wound on cores such that the weight of the roll must be supported by the cores rather than by winder drums, the supporting members in the form of chucks must fit tightly in the core so that an internal gearing effect does not take place.
Previously proposed designs of expanding chucks provided for expansion by means of a manually rotated screw thread which had to be carried out before winding took place. Other forms of core chucks used a wedging action of tapered pieces which slid up inclines by means of axial thrust exerted on the cores. In such devices, friction became a factor which prevented them from functioning as required.
Most expanding core chucks of the prior art used segmented pieces on the order of 3 or 4 which expanded radially away from each other. These pieces had to be retracted or held in place by means of a garter spring, a circular coil spring, or a rubber retainer. The relatively small number of outwardly expanding elements tended to make the cores go out-of-round in quadrants of the core, necessitating a reworking of the cores to make them round before they could be used again.
An improved form of expansible chuck is shown in U.S. Pat. No. 3,623,741 to Reeder et al, and assigned to the assignee of the present application. This chuck had a plurality of elongated chucking members disposed about a rotatable central camshaft. Radial expansion was achieved by simultaneous outward movement of the members relative to the rotational axis of the camshaft. Each of the chucking members had two spaced coaxially mounted yokes supported by corresponding circular cams located along the camshaft and offset from its rotational axis. A positioning ring concentric with the chuck axis was provided with radial guide pins to maintain the chucking members in equally spaced angular relation to each other as they moved outwardly in unison as a result of torque developed between the camshaft and any of the chucking members.
Another improved chucking device was described in Lucas U.S. Pat. No. 3,797,772 also owned by the assignee of the present invention. This patent described an expansible chuck having a spindle and a chuck bearing housing freely rotatable on the spindle. The bearing housing had external frusto-conical surfaces engaged by spaced internal frusto-conical segments on the insides of chuck leaves, and being guided in the chuck bearing housing for movement therein. An externally threaded member was provided which was connected with the chuck leaves to cause translational movement of the chuck leaves upon turning of the threaded member. Locking means were provided to engage the threaded member and hold it from rotation relative to the chuck bearing housing, to hold the chuck leaves in position.